Chemical Tests Flashcards
Sources of error in reagent strips
- Not mixing specimen
- Strip staying in urine for an extended period (may leech reagents from the pads)
- Excess urine on the strip can produce run over on adjacent pads
- Reaction timing
- Good light source
- Specimens of been refrigerated must be allowed to return to room temp as the enzymatic reactions are temperature dependent
Spciemen pH
A pH above 8.5 is associated with an improperly preserve specimen and indicates a fresh specimen should be obtained
Sulfosalicyclic Acid Precipitation Test
Cold precipitation test that reacts equally with all forms of protein, all precipitation tests must be performed on centrifuged specimens to remove any extraneous contamination.
Albumin:Creatinine Ratio
Comparing the albumin excretion to the creatinine excretion, the albumin reading can be corrected for overhydration and dehydration in a random sample
Microlbuminuria: 30-299 mg/g
Macroalbuminuria: >299 mg/g
Nephrotic Syndrome: >3.5g/day
Glucose Oxidation Interferences
Strong reducing agents such as ascorbic acid that prevent oxidation of the chromogen in the reagent strip
Clinitest Procedure and Problems
Tablets contain copper sulfate, sodium carbonate, sodium citrate, and sodium hydroxide. Upon addition of the tablet to water and urine, heat is produced by the hydrolysis of sodium hydroxide and it’s reaction with sodium citrate, and carbon dioxide is released from the sodium carbonate to prevent room air from interfering with the reduction reaction. After the reaction the tube is gently shaken and the color ranging from blue to orange red can be compared with the manufactures color chart
High glucose levels of phenomenon known as “pass-through” may occur, the color produced passes through the orange red stage and returns to green brown
Ketones
Testing is most useful for monitoring type one diabetes mellitus, ketonuria shows a deficiency of insulin indicating the need to regulate doses
Blood Reagent Strip Pattern
In reagent strip testing for blood the speckled pattern comes from blood cells lysing as they come into contact with the pad
False negative reactions can result when urine with a high specific gravity contains crenated red blood cells that do not lyse when they come in contact with the reagent pad
Ictotest
A confirmatory test for bilirubin consisting of testing mats and tablets containing nitrobenzene, SSA, sodium carbonate, and boric acid
Colors other than blue or purple appearing on the mat are considered to be a negative result
Nitrate Test
Detects initial bladder infection, because patients are often asymptomatic or have a vague symptoms that would not lead the physician to order a urine culture, chemical basis of the test is the ability of certain bacteria to reduce nitrate to nitrite which does not normally appear in urine
Leukocyte Esterase Test
Test the presence of Esterase in the granulocytic white cells, but not lymphocytes; presence of strong oxidizing agents or formalin in the collection container causes false positive reactions
Reagent Strip Reaction: Bilirubin
Reagent Strip Reaction: Blood
Reagent Strip Reaction: Clinitest
Reagent Strip Reaction: Creatinine
Reagent Strip Reaction: Glucose Oxidation
Reagent Strip Reaction: Ketones
Reagent Strip Reaction: Leukocyte Esterase
Reagent Strip Reaction: Nitrite
Reagent Strip Reaction: pH
Reagent Strip Reaction: Protein
Reagent Strip Reaction: Urobilinogen
Has interference from porphobilinogen
